Q: Safari bookmark sync (continuity) does not work anymore

I noticed that my Safari stopped syncing between devices.

I have Safari enabled in iCloud settings on all my devices (two Macs with OS X 10.10.2; one iPad Air 2, and one iPhone6, both with iOS 8.2).

I also tried the usual disable-enable-merge cycle, with more than 1 minute wait-time in between for the syncing to fully complete.

In the end, each device still has its own version of the bookmarks and reading list.

It used to work when running OS X 10.0 and iOS 8.1.

I don't know when this has changed.

Please help here.